There are different types of doors providing access to the aircraft, depending on the type of aircraft. The door is adapted to the size of the aircraft, for example. On an aircraft for transporting passengers, the doors used by passengers to board and disembark will not be the same as those used to load and unload luggage. It is also possible for the emergency exit doors to have a structure different from that normally used for boarding.
The invention relates more particularly to aircraft doors pivoting about a substantially horizontal axis (when the corresponding aircraft is on the ground, of course), meaning doors where the weight of the door opposes the operation of the door as it opens and closes. Even more particularly, the invention relates to doors intended for the passage of passengers. There are aircraft passenger doors which open downward and which may integrate a staircase providing access to the aircraft. This type of door is primarily on passenger aircraft for business travel and/or intended for transporting several dozen passengers. Passenger doors that open upward are found, for example, above the wings of an aircraft and are usually provided as emergency exits only.
It is known in the field of aeronautics or in other fields to use one or more gas springs to facilitate opening—or also closing—a door, a hood, a cover, or the like, and/or to hold it in the open position.
In the prior art, it is known to associate a damper having a plurality of gas or coil compression springs in order to damp the opening of the corresponding door, where the springs compensate for the weight of the door.
In a field unrelated to aeronautics, document US-2006/0180418 shows a cylinder in which two pistons slide. A first piston comprises a piston head and a piston rod and divides the cylinder into two chambers filled with hydraulic fluid. A second piston is a “free” piston separating one of the chambers filled with hydraulic fluid from a chamber filled with gas. The fluidtightness between the chamber filled with gas and the neighboring chamber filled with hydraulic fluid is achieved by a gasket placed between the second piston and the inner wall of the cylinder. As the second piston is intended to move within the cylinder, leakage of gas from the gas-filled chamber cannot be prevented, inevitably modifying the characteristics of the system described and presented in that document.
Document DE 297 02 927 U1 relates to a gas spring damped by a fluid intended more particularly for a bicycle suspension. Here, a gas-filled chamber is separated from the hydraulic fluid used for damping, by a flexible membrane. A valve (denoted by the reference 16) is provided to allow adjusting the pressure within the gas-filled chamber, for example using a bicycle pump.
In aeronautics, document EP 0 876 954 B1 illustrates, particularly in its FIGS. 3 and 9 (see § [0019]), the use of a damper mounted between two compression springs to assist with opening an aircraft door.